Elke ScholtenWageningen University

Food Physics group

Molecular Gastronomy

Molecular Gastronomy?

Gastros (Gr) = stomachNomos (gr) = knowledge or lawMoles (Latin) = small unit of mass

Classic: Molecular laws on the stomachModern: Molecular laws on the pleasure of eating

Hervé This: Molecular Gastronomy

Harold McGee: On food and Cooking

Understanding of phenomena in cooking:-Flavor / color (chemistry)-Structure (physics)-Sensation (psycology)

Food and art

Craft: Art- Repetition - innovation- Tradition - creativity- Technical - expression

Presentation

versus

Interplay between flavor and texture

Restaurants

El bulli, Barcelona: Ferran AdriaFat Duck, London: Heston Blumenthal

Number 1 in the world:Noma, Copenhagen: Rene Redzepi

2011:Dutch restaurants in top 50:Oud Sluis, Sluis: Sergio Herman (19)Librije, Zwolle: Johnny Boer (37)

Food!

Science in food

Creation/art:New Cooking Processes

Tools, Innovation,Creativity

Physiology and Psychology

Technology/Science

Science in food

Building blocks for food

Three main food structures:

- Emulsions- Gels- Foams

How can you control structures with the available building blocks ?

Science in food

Building blocks for food Dispersed phase

Continuous phase

gas liquid solid

Gas -- Aerosol (fog) Aerosol (smoke)

Liquid Foam (beer)

Emulsion (mayonnaise, milk)

Suspension / dispersion(starch solution)

solid Foam (bread)

Emulsion(cheese)

--

Food structures - Emulsions

Mixture of two immiscible liquids, such as oil and water

Droplets of oil in water

Not stable: add ingredientsto make it stable

egg: contains protein

Emulsions

Can be found in:- Milk- Meat- Fish- Eggs- Gelatin

No stabilizer

Building blocks :- Proteins- Oil (fat)- Water

Mayonnaise

Recipe: egg yolk, salt, mustard, pepper, vinegar, olive oil

Egg yolk: provides the protein: stabilizerMustard, pepper: tasteVinegar: pH low Oil: oil droplets in water. The more and smaller the oil droplets,

the thicker the mayonnaise (creamier)

How to make the mayonaise?- Adding the oil to the water and whisking very rapidly

Other ingredients:- proteins: egg yolk, egg white, gelatin- pH: any liquid that has a low pH: coke, orange juice, etc- Oil: other ingredients that have oil in them

Mayonnaise variations

Yolkless mayonnaise: egg white, oil, vinegar (pH)

Eggless mayonnaise: add the oil to a warm gelatin solution. The gelatin will gel upon cooling

Chocolate mayonnaise: replacing oil by chocolate fat, egg white Creamy texture

Heating in microwaveProteins will glue to each other more Chocolate cake

Orange mayonnaise: orange juice, gelatin, oil

Protein interaction

Positivecharges

Negativecharges

Protein is a spherical entity with a certain charge

Protein interaction

Low pH: more positive chargeH3O+

high pH: more negative chargeOH-

Every protein has a different iso-electric point: Depending on the pH, a protein is negatively or positively

charged.

+

++

+ +

+

pH

- -

--

-

-

-

Protein interaction

+

+

+

+ +

+

pH

--

-

-

-

-

-

+

+

+

+

+

+

Distance between proteins is determined by the amount of charge and thus by the pH

Charge density: double layer

Effect of pH:

Effect of salt:

Protein interaction

+

+

++

+

++

+

+

+

+

++

+

++

+

+

+

+

+

+

Aggregation of proteins

+

+

++

++

--

--

-

+

+

++

++

--

--

-

Aggregation of proteins

Unfavorable for stability

Is it dangerous or is it safe?

Baileys + tonic

+ ?

Baileys + tonic

Cream: fatStabilized by milk proteins

Addition of tonic

Change in pHaggregation of proteins

Creaming and coalescenceof oil droplets

Baileys + tonic

Oil layer on top of protein solution

CO2

Oil layer starts to foam

Is it dangerous or is it safe?

Baileys + tonic

Food structures - Foam

A substance that is formed by trapping many gas bubbles in a liquid or a solid

- Bread (air in solid)- Cake- Ice cream (air in water / ice)- Beer foam- Cappucino foam (milk foam)- Mousse- Meringue

No stabilizer

Food structures - Foam

A substance that is formed by trapping many gas bubbles in a liquid or a solid

- Bread (air in solid)- Cake- Ice cream (air in water / ice)- Beer foam- Cappucino foam (milk foam)- Mousse- Meringue

Building blocks :- Proteins- Water- Air- Fat

Solid fat proteins

Foams

Cappucino foam:The more protein/fat the milk has, the more stable the foam

Meringue: crispy sweet egg white foam

Only need proteins to make a foam:Gelatin instead of milk or egg proteins

Cucumber foamOther vegetable foams and fruit foamsPeanut butter foam, parmesan foam

Wine foamChampagne foam

ESPUMA

Foams

Coffee espuma

Champagne espuma

Mango and forest fruit espuma

Coke + Mentos?What happens?

Coke + Mentos?

Coke contains CO2 bubbles.

Growth of bubbles depends on thermodynamic parameters

Need energy to grow

23 43

4rrG

What happens?

Coke + Mentos?What happens?

Add mentos?

Porous material lots of small cracks and sites.

Lowers the energy to let bubbles growPorous sites and cracks act as nucleation

sites for bubble growth.

(nucleation and growth)

Speed depends on the energy and the amount of nucleation sites

Beer and fish?What happens?

Beer and fish?

Addition of fatty substances:- Lipids are small molecules

Competition between components:kinetics: smaller molecules adsorb faster

Foam - ice cream

Ice crystals : 30%(frozen water)

Air50%

Fat

air

proteins

Creamy ice cream:- Fat 5%- milk 75%

(proteins, water)- Sugar 20%

Sorbet ice- water / fruit 75%- Sugar 25%- stabilizer (gelatin)Sugar molecules:

Anti-freeze effect

Building blocks :- Water / ice- Air- Fat- Sugar- Proteins

Foam - ice creamRecipe: milk, cream, sugar, airFat and proteins: stabilizersSugar: anti-freeze substance determines the ratio between solid ice

and liquid water

Adding sugar: changes chemical potential of water:

At a certain temperature, chemical potential of ice is in equilibrium with the chemical potential of the sugar solution

Amount of sugar determines the freezing point depression (equilibrium between ice and solution – melting /freezing point)

iM

mKT

solute

soluteKF

A

L

ALA xRT ln0

A

L

A

S

A xRT ln00

Foam - ice cream

Sugar is not the only anti-freeze agent:- alcohol- salt

iM

mKT

solute

soluteKF

Foam - ice cream

Amount of sugar (or alcohol / salt) determines the percentage of solid ice:

0

10

20

30

40

50

60

70

80

-20 -15 -10 -5 0

temperature (ºC)

ice

frac

tio

n (

wt.

%)

200

300

400

1000

1001000

1000%

iK

MTiK

MT

m

K

solute

K

solute

soluteice

Freezer temperature

During eating, the amount if iceDecreases

Sensory perception(coldness, smoothness, etc)

Different anti-freeze agent:Different ice curveDifferent sensory perception

What do you need to make ice cream?- Water - Stabilizer (fat, protein, gelatin)- Anti freeze substance (sugar, gelatin,

alcohol, salt)

Wine ice-cream / liquor ice cream:- fruit: water, sugar (anti freeze)- Alcohol: water (anti-freeze)- Stabilizer (cream, gelatin)

Vegetable/meat ice cream:- vegetable: water- Fish/ meat: proteins, fat- No sugar: other stabilizer

(gelatin)

Foam - ice cream

Wine ice-cream Caipirinha ice cream

Garlic ice-creamshrimp ice-cream

Ice cream - new dishes

Tomato and basil sorbet ice

- 5 tomatoes- 120 ml lemon juice- 1 spoon of salt (anti freeze)- 70 ml water- 70 gram sugar (anti freeze)- tomato puree- chopped basil- gelatin (to stabilize the air)

Ice cream - new dishes

Egg and bacon ice cream

Fat duck, London

- 300 gram bacon- 1 liter milk (water, proteins)- 25 gram milk powder (proteins, fat)- 24 egg yolks - 125 gram glucose (anti freeze)

Gels

Gels are materials that are elastic and they have properties in between a solid and a liquid state

- Cheese- Gummy bears- Cooked egg

There are two types of gels:- Protein gels (eggs, meat)- Polysaccharide gels (desserts)

Protein gels

Gels are materials that are elastic and they have properties in between a solid and a liquid state

Scrambled eggs?

The temperature has an effect on the structure of an egg

Why?

Protein gel - Eggs

Protein is folded

when temperature increases they unfoldthey form crosslinksresults in a gel

The strength of the gel depends on the temperature

Network Gel

Protein gel - Eggs

The perfect egg!!

The protein in egg white (albumin) unfolds at 65CThe protein in egg yolk unfolds at 70C

An egg cooked between 65 C and 70 C

Protein gel - Meat

Meat

Meat contains a lot of proteinsWhen heated the proteins willunfold and cluster together

40C: unfolding proteins50C: muscle contracts55C: myosin clusters66C: other proteins cluster70C: myoglobin looses oxygen: turning pink79: actin clusters80C: meat becomes grey100C: water evaporates150C: chemical reactions

Polysaccharide gel

Polysaccharides are multiple sugars which form large chains.

Starch:

Other sugars:

amylose

amylopectin

Agar (seaweed)

Pectin: fruitCarrageenan: seaweedAlginate: algae

Xanthan

Polysaccharide gel

Polysaccharides are multiple sugars which form large chains.

Sugar network Gel

- Brittle gels- Elastic gels

Parameters that influencegel strength:

-Salt-pH-Specific ions

Polysaccharide gel

Effect of:-pH-salt

Groups that can become positive

Groups that can become positive

pH determines amount of charge determines the distance between the molecules

Salt decreases the effect of charge

Polysaccharide gelEffect of:-Specific ions

Calcium (positive) interacts with charges on alginate (negative) They form a network which is very strong

Negative charges

alginate

Polysaccharide gel

Gels:

- Fruit gels (water – sugar)- Foam gels (water – air –

sugar)

- Juices- Alcohol

Edible cocktail:

Martini-blueberry

Science in food

Building blocks for food By controlling amount of

building blocks one can play with the physical properties of food:

- Gel like- Incorporation of air (foams)- incorporation of oil (emulsions)- Controlling amount of ice

Defines the structure of food!

New ingredients

Spherification line

Gelification line

Surprise line

El Bulli: Texturas

New dishes

Spherification line

Liquid pea ravioli

Algin: alginateCalcic: calcium

alginate with calcium gel

Solution of peas, water, mint and algin

Dip into water with calcic

Outside will turn into a gel

New dishes

Spherification line

Fruit caviar:

melonorangelemon

New dishes

Spherification line

Melon caviar in a ham consomme

New dishes

Gelification line

Gellan: gelatinagarKappa/iota: carrageenan

They all form networks and therefore a gel

ribs underneath a beet-juice and campari gel

Expectation

Expectation

Egg

vanilla ice cream on mango

Expectation

Mango ravioli on a bed of coconut

Mango ravioli made by spherification With alginate and citric

Coconut gel is made by adding agar or carrageenan

Expectation

mustard ice cream withgel of olive oil and a foam of vinegar

Expectation can lead to a different flavor sensation

questions

?